5.12.9VUI and SEI messages (9)
The software coordinator mentions in the track B session that currently no software implementation of VUI elements exists, and it would be desirable if experts proposing VUI elements would also take action to implement them.
5.12.9.1Video usability information (VUI) (1)
JCTVC-J0287 Additional sample_ratio_idc values for square samples [Arturo Rodriguez (Cisco)]
This document proposes new aspect_ratio_idc values for signaling square samples with a sample scale factor other than one. A number of video applications require support for bitstreams in which the picture resolution may change from one coded video sequence (CVS) to the next, while maintaining constant the 2D size and aspect ratio of the spatial span implied by the output pictures of the successive coded video sequences (CVSs). In order to maintain the same implied spatial span from the output pictures of two consecutive CVSs with square samples but different picture widths and heights, the aspect_ratio_idc values of the two consecutive CVSs would need to be different. It would also facilitate entering the bitstream at the RAP (random access point) picture corresponding to the start of a CVS in which the picture resolution changes but the sample aspect ratio does not.
Presentation not uploaded.
It is proposed to use aspect_ratio_idc = 17, 18, and 19 to signal the following square samples with a sample scale factor not equal to one: 2x2, 1.5x1.5, 2/3x2/3.
Alternative: Define sample_scale_factor for the values above
Purpose: Tell the display how to output content that is downsampled – i.e. to upsample and display at higher resolution in anticipation of later higher-resolution content in the same stream.
Several experts raised doubts that this requires description in VUI, and what the benefit would be.
It was remarked that in some scenarios it could be possible to send some signal in the system layer or SEI.
For further study.
No action.
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